1. Field
The following description relates to a semiconductor device, and more particularly, to a micro-bolometer type infrared (IR) sensing device.
2. Description of the Related Art
A micro-bolometer type infrared (IR) sensing device senses IR light by detecting variation in a secondary attribute that responds to the heat absorbed when the IR light is applied thereon. One of the secondary attribute that is sensed is the TCR (Temperature Coefficient of Resistance). In conventional resistive-type sensing devices which take advantage of the TCR of the material, a resistive-type sensing part is made of Vanadium Oxide (VOx), poly-silicon, armorphous-silicon, thermistor ((MnNiCO)3O4), etc. These materials have an advantage that the TCR (ratio of resistance variation to temperature variation) is high, however they have a disadvantage that performance seriously deteriorates at low frequencies due to excessive flicker noise (that is, 1/f noise) caused by their inherent characteristics.
Also, such a conventional IR sensing device sometimes includes a chopper for resetting a sensing part by periodically blocking heat in the form of the thermal image that is incident on the array. However, the chopper limits the operation of the IR sensing device, and makes the construction of the IR camera system more complicated and increases manufacturing costs.
Conventional IR sensing devices have an inherent design conflict between sensitivity and image lag. To increase the sensitivity of the device each pixel must be as thermally isolated from it's environment as much as possible. A pixel that is very isolated from its environment is by design very slow to respond to changes in the scene and thus induces image lag. This new sensor has pixels that have thermal reset, thus allowing for the decoupling of sensitivity to the thermal time constant requirements of video frame rates. The thermal resetting action of this new device eliminates image lag and allows for an additional increase in sensitivity due to the elimination of the so called “Temperature Fluctuation Noise” component in the noise equations.
The present applicant has proposed a semiconductor device in which crystalline silicon thin film formed by a SOI (Silicon On Insulator) substrate manufacturing method is used as a sensing part, and a sensing structure part having a serpentine shape discharges heat by touching a substrate spaced apart downward from the sensing structure part, which has been registered as Korean Patent No. 704,378.
The semiconductor device is an improvement on conventional technologies in view of sensitivity, simplicity of structure and manufacture and elimination of image artifacts like image lag.